How do we know that Jesus' death on the cross was effective?

The effectiveness of Jesus' death on the cross is rooted in the divine purpose of God, as reflected in scriptures such as John 6:37, which assures that all the Father gives to the Son will come to Him. This promise indicates that Jesus' sacrificial death secured the redemption of all His elect, fulfilling the divine covenant. When He proclaimed 'It is finished' upon the cross, He confirmed that the price for sin had been fully paid, thus ensuring that no one chosen by God would be lost. The resurrection further validates the effectiveness of Christ's sacrifice, showing that He overcame the consequences of sin and death, guaranteeing eternal life for His people. This assurance of salvation rests firmly on the fulfillment of God's promises and the doctrine of unconditional election.